A vehicular powertrain mount assembly is usually known as an engine mount, a transmission mount, or the like. When an internal combustion engine powers a motor vehicle, there are numerous vibrations set up such as jounce vibrations, fore and aft vibrations, and torque and torque reaction vibrations. It is a customary practice to isolate these vibrations from the passenger compartment by using resilient powertrain mounts. Powertrain mount assemblies are also used to support a powertrain member on a vehicular frame to provide for jounce and roll control of the powertrain member relative to the frame. In a conventional powertrain mount assembly, two or more bracket members are bonded to a volume of a resilient material by adhesive means. The bracket members are normally stamped cold-rolled steel parts which can be attached by mechanical means to either the powertrain member or the frame member of a vehicle. A typical resilient material used in a powertrain mount assembly as a rubber material capable of absorbing most of the vibration from the powertrain member and the jounce from the frame member such that they are sufficiently isolated from each other. The type of rubber materials normally used are natural rubber, styrene-butadiene rubber, ethylene-propylene-diene-monomer rubber, and any other suitable elastomeric materials.
The bonding of the rubber material to the metal bracket is ordinarily accomplished with a solvent-based adhesive that is applied to the metal prior to the rubber molding process and then co-vulcanized with the rubber during the cure cycle. This is frequently called an in-mold bonding process. Numerous problems are associated with the in-mold bonding process and its resulting product. A first problem is the costly rubber-removal operation. In a contemporary mount design with complicated rubber block shapes and interlocking structures, it is impossible to seal rubber from certain forbidden areas. Subsequent operations to remove the unwanted rubber are labor intensive. Moreover, a secondary phosphating operation is required to replace the phosphate coating removed with the rubber flash.
Secondly, in an in-mold bonding process, metal brackets must first be placed in a mold cavity prior to the rubber vulcanization process. This greatly reduces the number of cavities allowed in a given mold size. The mold is frequently damaged from improperly positioned metal brackets. Furthermore, the mold cycle time of the mount assembly is increased because cold brackets must first be heated in the mold.
Thirdly, there is a significant amount of solvent emissions from the in-mold bonding process due to the solvent-based adhesive used. In most cases, the use of expensive recovery equipment is necessary to meet air pollution regulations.
It is therefore an object of the present invention to provide a powertrain mount assembly that can be bonded together after the rubber block is first vulcanized.
It is another object of the present invention to provide a post-vulcanization bonded powertrain mount assembly that can be bonded together by an inexpensive process suitable for use in a production environment.
It is yet another object of the present invention to provide a post-vulcanization bonded powertrain mount assembly comprising two bracket members and a volume of a rubber material sandwiched between and bonded to the two brackets by an epoxy adhesive.